#include <iostream>
#include <algorithm>
#include <math.h>
#define int double
using namespace std;


struct item{
	int m,v;
};


bool cmp(item a,item b){
	return (a.v/a.m)>(b.v/b.m);
}


signed main(){
	signed n,t;
	double ans=0;
	cin>>n>>t;
	item a[n];
	for(signed i=0;i<n;i++)
		cin>>a[i].m>>a[i].v;
	sort(a,a+n,cmp);
	signed k=0;
	while(t > 0  &&  k < n){
		if(t<a[k].m){
			ans += (a[k].v/a[k].m)*t;
			break;
		}
		ans += a[k].v;
//		cout<<a[k].v<<endl;
		t -= a[k].m;
		k++;
	}
	printf("%.2f",ans);
	return 0;
}
